This invention relates to flexible ducting and, more particularly, relates to an apparatus and method for manufacturing such flexible ducting and is an improvement over U.S. Pat. No. 4,351,682.
Flexible ducting for use in heating and air conditioning applications is constructed of a reinforcing wire formed into a helix covered by a plastic material. One method of manufacturing such ducting is to use an elongated mandrel and fabricate the ducting in predetermined lengths. A reinforcing wire is wound on the mandrel and a sheet of plastic is then laid over the reinforcing wire. Adhesive on the wire secures the reinforcing wire to the plastic sheet. The flexible ducting may then be covered with insulation and an outer sleeve to complete the assembly.
There are also machines in the prior art for continuously forming flexible ducting, in which a reinforcing wire is continously formed into a helix on a plurality of rollers or a mandrel which is simultaneously covered by continuous wraps of flexible strip material secured around the reinforcing wire with an adhesive. In one such device, reinforcing wire is wound on a plurality of supporting rollers mounted in circumferentially spaced relationship onto which the reinforcing wire and flexible strip material are fed to produce a flexible duct.
Another prior art device employs a cantilevered, free-wheeling mandrel which receives flexible strip material and reinforcing wire along a helical path with consecutive wraps of the flexible strip material forming a flexible duct with a continuous helical seam. Generally, the prior art devices require clinch rollers to drive and seal successive laps during use. They are also quite complex, and, although they provide means for manufacturing various diameter ducts, they are not readily adaptable for this purpose. Further, they are not readily adaptable for use with a variety of materials, and their rates of production (i.e., ft/min) is somewhat less than desirable.